1. Field of the Invention
The present invention relates to a photocurable and thermosetting resin composition capable of being pattern-formed by a laser oscillation light source of 350 to 420 nm in wavelength, a dry film using the same and a cured product thereof. More particularly, the present invention relates to a photocurable and thermosetting resin composition (i) capable of being pattern-formed by the laser oscillation light source of 350 to 420 nm in wavelength, (ii) exhibiting high sensitivity and having excellent resolving properties, and (iii) having excellent heat resistance, adhesiveness and electrical properties or the like, thereby being useful also as solder resist and capable of being developed by a diluted alkali solution, and a dry film using the same and a cured product thereof.
2. Description of the Related Art
In recent years, a direct writing method (laser direct imaging) using a laser beam as a light source has been put in practical use as a photo lithography method giving consideration to environment such as saving resources or energy saving. A direct writing device has features in which a mask manufacture process can be omitted and scaling can be applied to each substrate. The direct writing device is suitable for a multiproduct with a small lot, quick delivery and the manufacture of a multilayer circuit board.
Although the light source and wavelength of the direct writing device are replaced according to the application of the photo-curing resin composition to be used, the direct writing device is broadly classified into a type using a gas ion laser for the light source and another type using a solid laser for the light source. Argon gas is generally used in the gas laser, and a semiconductor laser and a YAG laser are used in the solid laser. When the direct writing device is classified according to the wavelength band of the laser emitted, the direct writing device is classified into an ultraviolet region type and a visible region type, and the wavelength bands of 355 nm and 488 nm are generally used.
As a resist which is adapted for the laser beam of 355 nm which is an ultraviolet ray region, a conventional known resist can be used, and for example, Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as JP-A-)2001-156328 (CLAIMS) or the like has been proposed. A resist which is adapted for a laser beam of 488 nm which is a visible light region is also conventionally known, and for example, JP-A-6-301208 (CLAIMS) and 2004-12635 (CLAIMS) or the like have been proposed as these resists.
Attention has been recently directed to a solid laser of 405 nm, and the solid laser has started to be used as a laser oscillation light source. Although the solid laser of 405 nm has small size, high efficient, low voltage, low power consumption and long life as compared with an argon gas laser, and a resist which is exposed at 488 nm as visible light must be used in a special environment under red light, the resist exposed at 405 nm has a feature in that the resist can be used in the existing environment under yellow light. Accordingly, the appearance of the laser cured composition having high sensitivity to the solid laser of 405 nm has been desired.
However, when the solder resist which is one of the photo-curing and thermosetting resin compositions conventionally used was exposed by using the direct writing device on which a semiconductor laser of 405 nm is mounted, a coating film could not be formed because of the insufficiency of curing. It is believed that since, when taking the energy for the laser output of 355 nm into consideration, the energy for the laser output of 405 nm is very low (respectively 4 W and 0.25 W), the insufficiency of curing is caused. Since the exposure energy exceeding at least 100 mJ/cm2 is required in order to cure the resin composition completely, a problem is generated in that the reduction of workability, i.e., the merit of quick delivery of the direct image forming method is lost.
In order to cure the resin composition completely in low exposure energy, it is necessary to reduce the light absorption of the resin itself with the aim of photo-curing the resin composition efficiently. However, a problem exists in that the existing resin composition comprises a compound containing a benzene ring having a conjugate double bond with large light absorption in large quantity in order to improve heat resistance.